1.No "using namespace std;"

2.Clearly declare "private" inside of class. For example:

use 
```c++
class item{
    private:
    int price;
    public:
    getPrice();
}
```

instead of class
 
```c++
class item{
    int price;
    public:
    getPrice();
}
```


3.Declare inheritance type(public, private, protected) when using inheritance.

4.If not finished with code, add a TODO as comments.

5.Add comments to explain what you want to do.